Bridging-blocks for dynamo-electric machines.



No. 871,758. PATENTED NOV. 19, 1907. E. HEITMANN & F. W. YOUNG. BRIDGING BLOCKS FOR DYNAMO ELECTRIC MACHINES.

APPLIOATIOH TILED 00'1.18. 1906.

uuuu

"kind" w-- T m7 n I Inventors, Witnesses: Edward Heilmann W Frederick WXiun UNITED STATES PATENT OFFICE.

EDWARD HEITMANN, OF MONTCLAIR, AND FREDERICK WM. YOUNG, OF EAST ORANGE,

NEW JERSEY, ASSIGNORS TO GROCKER-WHEELER COMPANY, OF AMPERE, NEW JER- SEY, A CORPORATIONOF NEW JERSEY.

Specification of Letters Patent.

Patented Nov. 19, 1907.

Application filed October 18. 1906- Serial No. 339.437-

To all whomtit may concern:

Be it known that we, EDWARD HEITMANN, residing at M'ontclair, in the county of Essex and State of New J ersey, and FREDERICK WM. YOUNG, residing at East Orange, in the- Alternating current machines such as.

altcrnators and induction motors are more economical as regards material when designed with, slots which are entirely or partly -bridged at the surface by magnetic material.

Bridging of slots by magnetic material is also of importance in steam or gas-engine drivcn-alternators, since the driving torque lacks uniformity. An element of steadines" of vQBIfiblOH is secured by employing a rotor with solid poles in which currents are set up when such irregularities of driving torque occur, and so I furnish countertorque. But with such solid poles a practically uniform magnetic flux distnibution across the polar faces of the rotor must be secured to prevent heavy losses during normal operation. If a toothed core of laminated iron with windings between the teeth is used in the stator, if the slot is' not inconveniently narrow, means must be provided for a substantial magnetic closure of the slots above the windings.

Our invention relates to a means for effecting such closure, which in brief consists of the ei'nployinent of bridging blocks of cast iron or iron 'with similar electrical and magnetic properties which arose shaped. that' they will secure the required uniformity of distribution of magnetic flux without aflording a seat for harmful eddy currents.

A further object of this invention is to provide these bridging blocks of such form aswill be inexpensive of manufacture, easy to assemble and easy to secure firmly so that they will form with the core and windings a mechanically rigid structure.

In the accompanying sheet of drawings, which forms a art of this ap lication, Figure 1 is a. plan of a portion 0 a stator of an alternator showing portions of three windings set in slots of the laminated stator ring, and covered by bridging blocks embodying like cast iron.

our invention. Fig. 2 is a face view of a portion of the stator including three slots, windings therefor and bridging blocks, the windings being in section. Fig. 3 is a perspective view of a modifiedform of bridging block. Fig. 4 is a perspective view of one end of a wooden rod or wedge used with this second form of bridging block.

In the form shown in Figs. 1 and 2, our invention is illustrated in connection with a toothed armature A which forms the stator element of an alternating current generator. The core of the armature, as illustrated, comprises a number of groups of toothed lamina: suitably spaced for ventilation, The teeth are under-cut or dovetailed near their tips and bridging blocks B. engage the dovetail. spaces between the adjacent tcethof each,

roup of laminae above the windings V.

hese blocks are of magnetic material, as cast iron or malleable iron, which latter is in fact and is to beunderstood to be cast iron modified to a greater or less depth from the surface to reduce brittleness, or they may be of kinds of steel possessing high resistivity Such magnetic material is preferable, because, while having ample magnetic conductivity, it possesses considerab specific electrical resistance or resistivity, so that eddy currn ts will be damped. Fun ther to damp such currents, slits s, s may be cut into the blocks from the edges next to the teeth. These slits lie in the same direction as the lamina and are transverse tolsuch eddy currents asthe operation of the Ina-- chine would chiefly tend to generate. These slits consequently tend to break up such currents. The bulk of the material comprising each block lies along the two edges next to the armature teeth and each block may be said to consist chiefly of two parallel contacting members m m next to or in contact with the teeth and a thin web to which joins the contacting members. A sufficient magnetic ath to the tooth on either side is afforded for all lines of force entering thepolar surface of the block, thus making the bridged slot eguivalcnt to an inclosed slot. By reason 0 the thinness of the connecting web, the magnetic flux from one tooth to the next adjacent above the windings and due to the current in these windings, is reduced to a minimum, so that the reaetance of windings embedded in a bridged slot is as low or I nearly as low as that of windings embedded in a partly inclosed slot.

tion of eddy currents to a minimum. And

. there is also afforded space for the insertion of wooden or other rods for binding down the windings and fastening the blocks in the slots. Insulation'I, for which fiber or paper are suitable materials, or for which hard apan may be used, is placed between ,the blocks and the teeth. In the form illustrated, the blocks have each a length ,which is about equal to the thickness of a group of lammw, as this length forms a convenlent unit for handling, and less likely to be broken than a longer block in driving into place. There are as many blocks in each slot as there are groups of laminae com osing the armature core, so that there wil be a minimum of obstruction of the ventilating s aces between" groups of-"laminae by "the ocks. In each slot 8. wooden rod or'wedge R 1s driven under all (if the blocks in the slot and between the blocks and the windings,

cated in the slots above the and the arts are thereby firmly secured in place. hese rods or wedges the ends of the end-blocks of each slot and are tatpled to the windings.

In e for'm shown in Figs. 1 and 2 Ion i-' tudmal dovetail slots are provided in t e blocks to recelve the wooden rods or wed es. In the form shown in Figs. 3 and 4-the un ersides of the blocks are made concave and the wooden rods have one side rounded, so that they .blnd between the blocks and windings mstead of In the blocks chiefly.

hlle we have shown and described ourinvent on as applied to a machine inwhich the armature member forms the stator, .it will be cbylousthat it is also applicable to a machine having a rotating armature.

What we claim as new and desire to secure by Lettens Patent of the United States is:

1. The combination of a slotted dynamo- GlGCiJI'IC machine element, windingsrlocated 1n the slots, and cast iron brid ing blocks insulated from the element an consisting of parallel contacting members. joined by thin webs, substantially as described.

2. The combination of a slotted dynamoelectric machine element, windings located in the slots, and cast iron bridging blocks lowindings, substantially as described.

3. The combination of a slotted dynamoelectric machine element, windin s located in the slots, and bridgin blocks of magnetic material located in the s ots above the windings, the contacting edges of which are roject beyond material consisting of parallel cont-acting.

members transversely slotted and joined by thin webs, substantially as described.

6. The combination of a slotted dynamoelectric machine element, windings located in the slots, bridging blocks of magnetic material in each slot, grooved longitudinally,

and a non-conducting strip fitted in the grooves and connecting the bridging blocks in each slot, substantially as described.

7. The combination of a slotted dynamo- -eleetric machine element, windings located in the slots, brid ing blocks ofmagnetic material transverse y slotted and grooved longitudinally, and non-conducting stri s fitted in the grooves and connecting the I idging blocks in each slot, substantially as described.

8. The combination of a slotted dynamoelectric machine element, windings located in the slots, bridging blocks of magnetic material c'onsistin of parallel contactin members transverse y slotted and joined y thin webs, and non-conducting stri s fitted between the bridg' g blocks and t e windings, substantially as described. j

9. The combination of a slotted dynamoelectric machine element consisting of groups of laminae with ventilating spaces between the groups, windings located in the slots, and a series of bridging blocks in'each slot the ends of which are spaced apart opposite the ventilating spaces in the element, substantially as described.

10. The combination of a slotted dynamoelectric machine element consisting of groups of laminae with ventilating spaces between the groups, windings located in the slots, a series of bridging blocks in each slot the ends of which are spaced apart opposite the ventilating spaces in the element, and a non-conducting strip fitted between each series of bridging blocks and the windings, substantially as described.

Signed by us at East Orange, New this 17th day of October, 1906.

EDWARD HEITMANN. FREDERICK WM. YOUNG Jersey, 

